The present invention relates to an input/output terminal of a motor to be mounted on an electric-powered vehicle or an electromagnetic wave shielding structure by means of which an electric wire/cable is connected to an input/output terminal of general electronic equipment.
Usually, when an electric wire/cable is connected to an input/output terminal of an electric-powered vehicle, leakage of an electromagnetic wave from the electric wire/cable to the outside is prevented. Conversely, in order to protect the motor from the influence of an external electromagnetic wave, a motor case is grounded, thereby attempting to realize shield conduction.
FIGS. 3 and 4 show the structure of a shielded connector described in Japanese Patent Application Laid-Open No. 294344/2000 filed by the present inventor, as a typical example of a related-art shielding structure for shielding against an electromagnetic wave. In this case, an electric wire/cable to be connected to an input/output terminal of a motor is a shielded cable 1. The shielded cable 1 is formed by means of forming an insulator 3 so as to cover a conductor 2 through extrusion molding; wrapping around an insulator 3 a metal braid 4 serving as a conductive shielding sheet; and coating the insulator 3 with an outer sheath 5 through extrusion such that the braid 4 is sandwiched between the insulator 4 and the outer sheath 5 and embedded in the outer sheath 5.
The sheath 5 is peeled from a terminal portion of the shielded cable 1, thereby exposing the braid 4 and the insulator 3 located beneath it. Further, the insulator 3 is peeled, thereby exposing the conductor 2. Metal terminal 6 is connected to the thus-exposed terminal 2 by means of crimping. The exposed braid 4 is connected to a shielding terminal (shielding member) 7 which constitutes the shielded connector and is made of conductive metal. The shielding terminal 7 is fitted into and connected to a mount hole xe2x80x9cbxe2x80x9d of a mount element B, such as a motor case. The mount element B is grounded by a ground G, thereby effecting shield conduction of the shielded cable in the sequence of the braid 4- greater than the shielding terminal 7- greater than the mount element B- greater than the ground G.
FIG. 4 is a perspective view showing, as a single element, the shielding terminal 7, which is the primary member of the shielded connector structure. The shielding terminal 7 is a cylindrical element in which a step of different diameter is formed by means of drawing. The shielding terminal 7 is fixed to the outer periphery of the terminal portion of the shielded cable 1 by means of fitting and crimping. As illustrated, the shielding terminal 7 has a flange 7a provided at the upper end of the cylindrical element. A portion of the flange 7a is cut and raised, thereby forming a projection 7b. As shown in FIG. 3, the braid 4 is folded back and brought into contact, from the outside, with a lower portion of the cylindrical element of the shielding terminal 7 press-fitted around the outer periphery of the cable. A braid hold tube 8 covers the folded-back section of the braid 4 from the outside, thus fixing the folded-back section. Thus, the braid 4 is connected to the shielding terminal 7 in such a manner as to enable shield conduction.
As shown in FIG. 3, the shielded connector structure is provided with a housing 9 as one of the other primary components constituting the shielded connector structure, wherein the housing 9 is cylindrically formed from an insulating material or a conductive material such as aluminum. An engagement recess 9a is formed in the housing 9. The projection 7b formed in the shielding terminal 7 is engaged with the engagement recess 9a, whereby the shielding terminal 7 is positioned so as to remain stationary when the cable is rotated about an axis Cxe2x80x94C thereof. The flange 7a of the shielding terminal 7 that has been positioned so as to face such a specific direction is sandwiched between a flange section 9b provided on the housing 9 and the mount element B and secured by means of tightening a bolt into a bolt hole 7c formed in the flange 7a. As a result, the shielding terminal 7 is connected to the mount element B, thereby attempting to effect conduction.
As has been described above, in such a shielded connector structure, the shielding terminal 7 fitted around the outer periphery of the terminal portion of the shielded cable 1 is positioned on the housing 9 by means of the projection 7b. The shielding terminal 7 is connected to the mount element B in conjunction with the housing 9 by means of tightening a bolt. As a result, limitations are imposed on movement of the shielded cable 1 such that the cable 1 remains stationary when rotated about the axis Cxe2x80x94C thereof. Concurrently, the shielded cable 1 is limited so as not become axially dislodged. In this way, the shielded connector structure is set in the mount hole xe2x80x9cbxe2x80x9d of the mount element B.
The shielded connector structure shown in FIGS. 3 and 4 is susceptible to improvement in terms of the following points.
One point relates to a problem stemming from the shielding terminal 7 press-fitted to the outer periphery of the terminal portion of the shielded cable 1 being positioned stationary so as not to move along the axis Cxe2x80x94C thereof, by means of causing the projection 7b to engage with the housing 9. In short, the conductor 2 must be crimped such that the metal terminal 6 is spaced a predetermined access distance from the position where the shielding terminal 7 is secured, in agreement with the orientation of the shielding terminal 7 positioned so as to face a specific direction. Further, the conductor 2 must be crimped such that the terminal connection hole 6 is oriented toward an appropriate direction in preparation for connection with an input/output terminal of a motor.
If the metal terminal 6 is not press-fitted to the conductor 2 in an appropriate orientation and at an appropriate distance in agreement with the orientation and position of the shielding terminal 7, an access dimension and the orientation of the bolt hole 6b will become inappropriate, thereby imposing extreme difficulty on attaining connection with an input/output terminal of a motor. Thus, the operation for press-fitting the metal terminal 6 is uniquely limited in association with the shielding terminal 7. Hence, assembly operation must be performed with caution and discretion. Such inconvenience induces a remarkable drop in working efficiency.
Another point of the problems is that positioning the shielding terminal 7 by means of causing its projection 7b to engage with the engagement recess 9a of the housing 9 demands a high degree of machining precision; that is, the dimensional tie-in precision and positioning precision of the shielding terminal 7 and those of the housing 9, and a center-to-center dimensional precision of the shielding terminal 7 and that of the housing 9 with respect to the bolt hole used for tightening the mount element B.
The object of the invention is to provide an electromagnetic wave shielding structure capable of enhancing workability and improving the degree of dimensional-precision freedom of individual members, by means of obviating limitations imposed on the orientations and positions of individual members at the time of an assembly operation.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) An electromagnetic wave shielding structure comprising:
a cylindrical conductive shielding member secured to a shield cable, which includes a conductor and a braid surrounding the conductor, and electrically connected to the braid, the shielding member being rotatably attached to a mount hole of a grounded conductive mount element in a state in which the shielding member is secured to the shield cable;
a metal terminal connected to the conductor of the shield cable; and
a housing for housing a part of the shield cable and securing the shielding member to the mount element.
(2) The electromagnetic wave shielding structure according to (1), wherein the metal terminal can be secured to the conductor without involvement of limitations on a rotating angle of the metal terminal, other than setting a dimensional distance between the shielding member secured to the shielded cable and the metal terminal.
(3) The electromagnetic wave shielding structure according to (1), wherein
the shielding member includes a cylindrical portion electrically connected to the braid, and a tapered edge extending outwardly from the cylindrical portion,
the mount hole includes a tapered section which is brought in contact with the tapered edge when the shielding member is attached to the mount hole for preventing the shielding member from passing through the mount hole.
(4) The electromagnetic wave shielding structure according to (3), wherein the housing includes a portion which presses the tapered edge of the shielding member to the tapered section of the mount hole when the housing secures the shielding member to the mount element.
(5) The electromagnetic wave shielding structure according to (4), wherein the housing is fixed to the mount element by a bolt so as to press the tapered edge of the shielding member to the tapered section of the mount hole.
(6) The electromagnetic wave shielding structure according to (1), wherein the housing is fixed to the mount element by a bolt.
(7) The electromagnetic wave shielding structure according to (6), wherein
when the shielding portion and the housing is attached to the mount element in a state in which the housing is not fixed to the mount element by the bolt, the shielding member can be rotated with respect to the mount element, and
when the housing is fixed to the mount element by the bolt, the shielding member is secured to the mount element and is prevented from rotating.